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Etude de l'implication électrophysiologique des ganglions de la base lors de crises focales motrices chez le primate.

Annaelle Devergnas 1
1 Inserm U836, équipe 7, Nanomédecine et cerveau
GIN - Grenoble Institut des Neurosciences
Abstract : Motor seizures can be pharmaco-resistant but resective surgery, although possible, is usually not offer as a therapeutic option. Deep brain stimulation is supposed to be a promising therapy but requires better understanding of the physiology of new target such as basal ganglia (BG). Although BG have been proposed to be involved in the propagation and the control of seizure, the electrophysiological mechanisms underlying the control of seizure have not been yet elucidated. Here we aimed at determining the effect of neocortical seizures on BG structures involved in the motor loop (striatum, pallidum, STN and SNr). To address this issue, we developed a monkey model induced by cortical injection of penicillin. This model was very focal and had a good reproducibility. During interictal period, electrophysiological modifications were only found after the interictal spike. These spikes induced modification on unit activity and on LFP. Strong modifications were found during ictal period with an increase of the firing rate, a modification of the firing pattern, a hyper-synchronisation of cells and a coherence between the cortex et the BG activity. However, these modification wasn't similar between the different BG structures. We conclude that these major modifications constitute an evidence of BG reorganization during focal motor seizure. The cortico-subthalamo-nigrale loop seems to be implicated in the propagation of seizure whereas the cortico-putamino-pallidale loop seems to be more implicated in the control of seizure. The second part of the study had showed that the pathways implicated in seizure are specific to the type of the seizure. Indeed, the implication of the SNr and the caudate were more important during focal premotor seizure than during motor seizure. To conclude, this study a permit us to prove the implication of the BG structures during focal motor seizure and also to put in evidence the existence of further functional loops implicated in a different manner in the propagation and the control of this kind of seizure. . The fact that oscillatory frequency in the putamen and GPi differ with the cortical EEG frequency and that the coherence between GPi, the Putamen and the cortex appears only at the end of the seizure (especially for GPi, while it appears at the onset of the seizure for the STN and GPe) might create an imbalance between the direct and the indirect BG pathway at the onset of seizure, facilitating its propagation. Whether the modulation of BG will restore a balance between the 2 systems, leading to a cessation of the seizure, is still a scientific and therapeutical challenge.
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Submitted on : Wednesday, July 18, 2012 - 3:53:21 PM
Last modification on : Friday, November 6, 2020 - 4:04:15 AM
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  • HAL Id : tel-00718961, version 1


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Annaelle Devergnas. Etude de l'implication électrophysiologique des ganglions de la base lors de crises focales motrices chez le primate.. Neurosciences [q-bio.NC]. Université Joseph-Fourier - Grenoble I, 2009. Français. ⟨tel-00718961⟩



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